I'm trying to specialize a template method like this:
template <typename X, typename Y>
class A {
public:
void run(){};
};
template<typename Y>
void A<int, Y>::run() {}
But I get
main.cpp:70:17: error: nested name specifier 'A<int, Y>::' for declaration does not refer into a class, class template or class template partial specialization
I understand that the specialization isn't yet complete because I haven't instantiated it with a specific Y, but how can I do that?
You need at first partially specialize the class itself including the function declaration. After that you can write its definition. You may not partially specialize a function.
For example
#include <iostream>
template <typename X, typename Y>
class A {
public:
void run()
{
std::cout << "How do you do?\n";
};
};
template<typename Y>
class A<int, Y>
{
public:
void run();
};
template<typename Y>
void A<int, Y>::run()
{
std::cout << "Hello World!\n";
}
int main()
{
A<int, int>().run();
A<double, int>().run();
return 0;
}
The program output.
Hello World!
How do you do?